Some conventional fire protection systems employ the polling method which causes the fire control panel to circularly call the terminal units in order to read from each of the called terminal units state information (presence or absence of an abnormality signal from an abnormality sensor, or ON/OFF of the control circuits for devices to be controlled) or to control the called terminal units.
The above-mentioned terminal units may be slave units having abnormality sensors (fire detectors, gas sensors etc.) and/or controlled devices (fire doors, smoke control devices, smoke venting devices, fire extinguishing systems, etc.) connected. Alternately, the terminal units may be the abnormality sensors or controlled devices themselves.
In the above-mentioned fire protection system the identification of the terminal units to be controlled and the time needed for the control are stored in advance in a memory means, such as ROM's, in the fire control panel so that the fire control panel may control the appropriate terminal units on the basis of data stored in the memory means in case of an abnormality, such as a fire or gas leak.
Presently there are various terminal units to be controlled, and the time required for their control varies with each terminal unit. For example, fire doors, emergency doors, smoke venting dampers and smoke control dampers are kept locked in position by electric locks. The electric locks are released by actuating the control circuits in the slave units for about ten seconds. The door or damper moves to the predetermined positions with the aid of door closers or their own weight.
For opening, closing and resetting of a motor driven fire shutter, smoke venting damper, or smoke control/fire damper provided in the duct of an air conditioning system, it is necessary to operate the control circuits in the slave units for control of the motors, i.e. forward or reverse rotation of the motor for a certain length of time ranging from about ten seconds to a few minutes.
In case of a fire, the fire control panel (or control panel) sends the control start command to the terminal unit which is to be controlled and causes the control circuit in the terminal unit to operate. After the corresponding lapse of time required for control, the fire control panel sends the control termination command to the terminal unit to cease operation of the control circuit. As to these terminal units requiring reset of their controls after the extinguishment of the fire, the fire control panel sends the control start command at the time of reset start.
As can be seen from the above description, the time required for control varies, and this imposes a heavy workload on the fire control panel (or control panel) in the conventional system.
Moreover, there are also problems in that the contents stored in the memory means of the fire control panel need to be newly prepared for each installation of the fire alarm system and that whenever changes are made with respect to devices to be controlled, those stored contents have to be changed accordingly. Such preparation and changes are troublesome.